Normalize tuple fallback to tuple[Any, ...] in constructor if it isn't special

Author: sterliakov

mypy/checker.py

@@ -8485,11 +8485,6 @@ def visit_type_var(self, t: TypeVarType) -> bool:
         # multi-step type inference.
         return t.id.is_meta_var()
 
-    def visit_tuple_type(self, t: TupleType, /) -> bool:
-        # Exclude fallback to avoid bogus "need type annotation" errors
-        # TODO: Maybe erase plain tuples used as fallback in TupleType constructor?
-        return self.query_types(t.items)
-
 
 class SetNothingToAny(TypeTranslator):
     """Replace all ambiguous Uninhabited types with Any (to avoid spurious extra errors)."""

mypy/types.py

@@ -2415,6 +2415,12 @@ def __init__(
         implicit: bool = False,
     ) -> None:
         super().__init__(line, column)
+        if fallback.type and fallback.type.fullname == "builtins.tuple":
+            assert len(fallback.args) == 1
+            if not isinstance(fallback.args[0], AnyType):
+                fallback = fallback.copy_modified(
+                    args=[AnyType(TypeOfAny.implementation_artifact)]
+                )
         self.partial_fallback = fallback
         self.items = items
         self.implicit = implicit